An exemplary refractive-index sensor includes a photonic crystal microcavity structure, a light source, and a detector. The method may include forming a resistor pattern and a dummy gate electrode, which include polysilicon, and forming an impurity region adjacent to the dummy gate electrode. The ends of the pistons facing towards the swash plate are supported on the swash plate. The system also includes a field focusing element disposed between the first coil and the second coil and configured as a self resonant coil having a standing wave current distribution to focus the magnetic field onto the second coil and enhance the coupling between the first coil and the second coil. The switching circuit is coupled to the first oscillator and a second oscillator, and utilized for receiving a first oscillating signal generated from the first oscillator and a second oscillating signal generated from the second oscillator, and selecting one of the first oscillating signal and the second oscillating signal as the clock signal according to a status signal. Two different products can thus alternately be distributed separately or together.